EFFECT OF CROWDING ON SURVIVAL 189 



series of bunches which were run simultaneously. The means for 

 each of these are indicated for each point. The graph starts with 

 the rate given during the first 4 hours and proceeds with that given 

 during the different fifths of the experiments. This means of chart- 

 ing is used because of the varying length of the experiments to be 

 summarized, all of which were physiologically the same length, in 

 that they were terminated when the starving individuals being 

 tested had reached approximately the same degree of depression as 

 measured by death or by fragmentation of the arms. 



Graph B shows similarly the total mean oxygen consumption for 

 each group. The initial amount indicated is that which would have 

 been given had the animals continued to respire for a period equaling 

 the others in length but at the rate given in the first 4 hours of 

 experimentation. Again the solid line represents the isolated in- 

 dividuals and the broken line the bunched animals, and again the 

 spread of the means for each series of bunches is indicated. This 

 form of presentation shows at a glance the more rapid consumption 

 of oxygen in initial stages, particularly on the part of the isolated 

 individuals, in contrast with the reduced rate later. The increase in 

 the rate of respiration near the close of the experiment is due to 

 the greater consumption of oxygen in the process of autotomy and 

 to the inclusion of some cases in which decay of fragmented parts of 

 arms may have occurred. 



The isolated animals have a rate of oxygen consumption 186 per 

 cent above that of the groups during the first 4 hours. Later this 

 mean rate of consumption falls for both, but more rapidly for the 

 isolated than for the bunched individuals, so that, when the entire 

 course of the experiments is considered, the rate of use of oxygen 

 by the isolated animals is only 83 per cent of that of the accompany- 

 ing groups. The differences of these means have about the same 

 statistical value as that noted for the initial 4 hours of respiration. 



The foregoing statement and graph does not show the extent of 

 the difference between the oxygen consumption of the isolated and 

 the bunched animals, since, on the average, the former died off" more 

 rapidly than did the bunched individuals. The results reported here 

 are in terms of the mean oxygen consumed by the animals still liv- 



